1. Field of the Invention
The present invention relates generally to the fabrication of semiconductor wafers, and, more particularly, to high density plasma etching chambers having lining materials that reduce particle and metallic contamination during processing, and associated chamber lining structures.
2. Description of the Related Art
As integrated circuit devices continue to shrink in both their physical size and their operating voltages, their associated manufacturing yields become more susceptible to particle and metallic impurity contamination. Consequently, fabricating integrated circuit devices having smaller physical sizes requires that the level of particulate and metal contamination be less than previously considered to be acceptable.
In general, the manufacturing of the integrated circuit devices (in the form of wafers) includes the use of plasma etching chambers, which are capable of etching selected layers defined by a photoresist mask. The processing chambers are configured to receive processing gases (i.e., etch chemistries) while a radio frequency (RF) power is applied to one or more electrodes of the processing chamber. The pressure inside the processing chamber is also controlled for the particular process. Upon applying the desired RF power to the electrode(s), the process gases in the chamber are activated such that a plasma is created. The plasma is thus configured to perform the desired etching of the selected layers of the semiconductor wafer.
Typically, a processing chamber that is used for etching materials such as silicon oxides requires relatively high energies to achieve the desired etch result, compared to other films etched during fabrication. Such silicon oxides include, for example, thermally grown silicon dioxide (SiO2), TEOS, PSG, BPSG, USG (undoped spin-on-glass), LTO, etc. The need for high energies stems from the need to bombard and break the strong bonds of the silicon oxide films and drive chemical reactions to form volatile etch products. These chambers are therefore referred to as xe2x80x9chigh density oxide etch chambers,xe2x80x9d that are capable of producing high plasma densities in order to provide a high ion flux to the wafer and achieve high etch rates at low gas pressures.
While high density oxide etch chambers work well in etching the desired wafer surfaces, the internal surfaces of the etch chamber are also subjected to the high ion power. Therefore, material from the internal surfaces of the etch chamber is removed as a result of the ion bombardment by either physical sputtering or chemical sputtering, depending on the composition of the material and the composition of the etch gas.
Recognizing that the internal surfaces of the etch chamber are exposed to the plasma in high density oxide chambers, chambers are now designed to permit the use of simple lining parts, such as, disks, rings, and cylinders. Because these parts are configured to confine the plasma over the wafer being processed, these parts are continuously exposed and attacked by the processing plasma energies. Due to this exposure, these parts ultimately erode or accumulate polymer buildup, requiring replacement or thorough cleaning. Eventually, all parts wear out to the point that they are no longer usable. These parts are hence referred to as xe2x80x9cconsumables.xe2x80x9d Therefore, if the part""s lifetime is short, then the cost of the consumable is high (i.e., part cost/part lifetime).
Because these parts are consumables, it is desirable to have surfaces that are resistant to the plasma energies, which will therefore reduce the cost of the consumable. Prior art attempts to reduce the cost of the consumable have included manufacturing these parts from aluminum oxide (Al2O3) and quartz materials. Although these materials are somewhat resistant to the plasma energies, in high density oxide etch chambers, the high ion bombardment by the plasma has the down side of producing levels of contamination (e.g., particle contamination and metallic impurity contamination) that are less than acceptable. For example, if the surface of the consumable part is aluminum oxide (i.e., alumina), when the plasma bombards the surfaces, aluminum will be released and then will mix in with the plasma that lies above the wafer. Some of this aluminum becomes embedded in an organic polymer that is deposited on the wafer during etching and on the surfaces of the consumable parts (i.e., chamber liners, covers, and the like). When this happens, the polymer on the surface of the consumable parts may not be able to be completely cleaned during a conventional in-situ plasma clean or xe2x80x9cashxe2x80x9d step. Thus, a friable, flaking film or powdery coating that includes C, Al, O, and F is left behind after the in-situ plasma clean, and therefore results in high particle counts. The aluminum deposited in structures being etched and the films on the silicon wafer can cause degradation of devices subsequently formed, for example, by increasing leakage current in DRAM cells.
As mentioned above, quartz is also used as the material of the interior surfaces of the consumable parts. However, quartz surfaces have been found to be an unfortunate source of particles due to the low thermal conductivity of quartz and the high etch rates in high density plasmas used to etch oxides. Additionally, low thermal conductivity quartz makes surface temperature control of these parts very difficult. This results in large temperature cycling and flaking of the etch polymer deposited on the surface of the consumable parts, and therefore causes the unfortunate generation of contaminating particles. A further disadvantage of quartz consumable parts is that the high etch rate in high density oxide etchers tends to cause pitting in the quartz, which then results in spalling of quartz particles.
In view of the foregoing, there is a need for high density plasma processing chambers having consumable parts that are more resistant to erosion and assist in minimizing contamination (e.g., particles and metallic impurities) of the wafer surfaces being processed. There is also a need for consumable parts for use in high density plasma applications, and that are capable of withstanding temperature variations while preventing damage to the consumable parts.
The present invention fills these needs by providing temperature controlled, low contamination, high etch resistant, plasma confining parts (i.e., consumables) for use in plasma processing chambers. It should be appreciated that the present invention can be implemented in numerous ways, including as a process, an apparatus, a system, a device or a method. Several inventive embodiments of the present invention are described below.
In one embodiment, disclosed is a plasma processing chamber including an electrostatic chuck for holding a wafer, and having consumable parts that are highly etch resistant, less susceptible to generating contamination and can be temperature controlled. The consumable parts include a chamber liner having a lower support section and a wall that is configured to surround the electrostatic chuck. The consumable parts also include a liner support structure having a lower extension, a flexible wall, and an upper extension. The flexible wall is configured to surround an external surface of the wall of the chamber liner, and the liner support flexible wall is spaced apart from the wall of the chamber liner. The lower extension of the liner support is however, configured to be in direct thermal contact with the lower support section of the chamber liner. Additionally, a baffle ring is part of the consumable parts, and is configured to be assembled with and in thermal contact with the chamber liner and the liner support. The baffle ring defines a plasma screen around the electrostatic chuck. A heater is then capable of being thermally connected to the upper extension of the liner support for thermally conducting a temperature from the liner support to the chamber liner and the baffle ring. Also included is an outer support that is thermally connected to a cooling ring that is coupled to a top plate of the chamber. The outer support and the cooling ring are therefore capable of providing precision temperature control to the chamber liner, along with a cast heater. This precision temperature control therefore prevents temperature drifts, which therefore advantageously enables etching a first wafer with about the same temperature conditions as a last wafer.
In a most preferred embodiment, consumable parts including the chamber liner and the baffle ring are made completely from or coated with a material selected from silicon carbide (SiC), silicon nitride (Si3N4), boron carbide (B4C) and/or boron nitride (BN) material. In this manner, these materials, once exposed to the energy of the plasma sputtering, will produce volatile products that are substantially similar to volatile etch products produced during the etching of surface layers of the wafer.
In another embodiment, a plasma etching chamber having consumable parts is disclosed. The consumable parts include a chamber liner having a lower support section and a cylindrical wall that surrounds a center of the plasma etching chamber. A liner support that is configured to surround the chamber liner. The liner support is thermally connected to the lower support section of the chamber liner. The liner support further includes a plurality of slots that divide the liner support into a plurality of fingers. In a preferred embodiment, the chamber liner is made from a material selected from one of a silicon carbide (SiC) material, a silicon nitride (Si3N4) material, a boron carbide (B4C) material, and a boron nitride (BN) material, and the liner support is made from an aluminum material.
In yet another embodiment, a method for using consumable parts for use in a high density plasma etching chamber is disclosed. The method includes use of a chamber liner from a material selected from one of a silicon carbide (SiC) material, a silicon nitride (Si3N4) material, a boron carbide (B4C) material, and a boron nitride (BN) material. The chamber liner can have a wall that surrounds a plasma region of the chamber and a lower support section. The method can include use of an aluminum liner support optionally having a lower extension, a flexible wall and an upper extension wherein a plurality of slots are provided in the flexible wall and the lower extension of the liner support to enable the liner support to expand at elevated temperatures. The method optionally includes use of a baffle ring of silicon carbide (SiC), silicon nitride (Si3N4), boron carbide (B4C) and/or boron nitride (BN). A plurality of slots can be provided in the baffle ring to define a plasma screen. The method can include thermal control of the chamber liner via a thermal path through the liner support and the baffle ring.
According to an embodiment of the invention, a plasma processing chamber includes a chamber liner and a liner support, the liner support including a flexible wall configured to surround an external surface of the chamber liner, the flexible wall being spaced apart from the wall of the chamber liner. For purposes of optional temperature control of the liner, a heater can be thermally connected to the liner support so as to thermally conduct heat from the liner support to the chamber liner. Although any suitable materials can be used for the liner and liner support, the liner support is preferably made from flexible aluminum material and the chamber liner preferably comprises a ceramic material.
The liner support can have various features. For instance, the flexible wall can include slots which divide the liner support into a plurality of fingers which enable the flexible wall to absorb thermal stresses and/or a lower extension of the liner support can be fixed to a lower support section of the chamber liner. If desired, a baffle ring in thermal contact with the chamber liner and the liner support can be used to define a plasma screen around an electrostatic chuck located in a central portion of the chamber. The chamber liner and/or baffle ring are preferably made from one or more of silicon carbide (SiC), silicon nitride (Si3N4), boron carbide (B4C), and boron nitride (BN).
The plasma processing chamber can include various features. For example, the chamber liner can have low electrical resistivity and be configured to provide an RF path to ground. If desired, a gas distribution plate having high electrical resistivity can be provided over an electrostatic chuck and/or a pedestal supporting a focus ring and the electrostatic chuck. The gas distribution plate, the focus ring and/or the pedestal are preferably made from one or more of the silicon carbide (SiC), silicon nitride (Si3N4), boron carbide (B4C), and boron nitride (BN). The plasma can be generated in the chamber by an RF energy source which inductively couples RF energy through the gas distribution plate and generates a high density plasma in the chamber. The RF energy source preferably comprises a planar antenna. The chamber can be used for plasma processing semiconductor wafers. For example, the chamber can be a plasma etching chamber.
The liner can have various configurations. For example, the liner support can include an outer support thermally connected to a lower extension of the liner support and the outer support can be in thermal contact with a water cooled top plate mounted on the chamber. The liner support can also include an upper extension, a flexible wall, and a lower extension, wherein the flexible wall and the lower extension have a plurality of slots that define a plurality of fingers in the liner support. For temperature control, a cast heater ring can be located in thermal contact with the liner support, the heater ring including a resistance heated element which heats the liner support so as to thermally control the temperature of the chamber liner.
According to another embodiment of the invention, a semiconductor substrate is processed in a plasma processing chamber having a chamber liner and a liner support, the liner support including a flexible wall configured to surround an external surface of the chamber liner, the flexible wall being spaced apart from the wall of the chamber liner wherein a semiconductor wafer is transferred into the chamber and an exposed surface of the substrate is processed with a high density plasma. The chamber liner is preferably a ceramic material and the liner support preferably includes an outer support extending between the liner support and a temperature controlled part of the chamber, the outer support being dimensioned to minimize temperature drift of the chamber liner during sequential processing of a batch of semiconductor wafers. During wafer processing, the ceramic liner is preferably removed from the chamber and replaced with another ceramic liner after processing a predetermined number of semiconductor wafers. Further, the chamber liner can include a wafer entry port enabling passage of the wafer into the chamber.
Other aspects and advantages of the invention will become apparent from the following detailed description, taken in conjunction with the accompanying drawings, illustrating by way of example the principles of the invention.